I did run across this at the SSA website:
Spouse’s benefits
A spouse who has not worked or who has low earnings can be entitled to as much as one-half of the retired worker’s full benefit. If you are eligible for both your own retirement benefits and for benefits as a spouse, we always pay your own benefits first. If your benefits as a spouse are higher than your retirement benefits, you will get a combination of benefits equaling the higher spouse benefit.
If you have reached your full retirement age, and are eligible for a spouse’s or ex-spouse’s benefit and your own retirement benefit, you may choose to receive only spouse’s benefits and continue accruing delayed retirement credits on your own Social Security record. You may then file for benefits at a later date and receive a higher monthly benefit based on the effect of delayed retirement credits.
If you are receiving a pension based on work where you did not pay Social Security taxes, your spouse’s benefit may be reduced. Additional information on pensions from work not covered by Social Security can be found in Pensions from work not covered by Social Security
If spouses want to get Social Security retirement benefits before they reach full retirement age, the amount of the benefit is reduced permanently. The amount of reduction depends on when the person reaches full retirement age.
For example:
If full retirement age is 65, a spouse can get 37.5 percent of the worker’s unreduced benefit at age 62;
If full retirement age is 66, a spouse can get 35 percent of the worker’s unreduced benefit at age 62;
If full retirement age is 67, a spouse can get 32.5 percent of the worker’s unreduced benefit at age 62.
The amount of the benefit increases at later ages up to the maximum of 50 percent at full retirement age. If full retirement age is other than those shown here the amount of the benefit will fall between 32.5 percent and 37.5 percent at age 62.